How to say "unthinkable" in Japanese

• とんでも無いとんでもないJLPT N3approx.Common
  i-adjectiveCovers 'unthinkable' in the sense 'absurd, outrageous': something so wrong it should not even be considered. Very often an exclamation flatly rejecting a suggestion or statement, and it also covers 'unexpected'.
  ジャックが音楽おんがくが苦手にがてなんてとんでもない、それどころか、ピアノを弾ひくのがうまい。↗

  It isn't true that Jack is no good at music; on the contrary, he plays the piano well.
• 心外しんがいCommon
  na-adjective, nounCovers 'unthinkable' as 'wholly unexpected', with a personal nuance of hurt or disappointment, typically at another person's words or attitude toward you; it is not the word for 'unthinkable' meaning 'impossible'.
• ありえないCommon
  i-adjectiveCovers 'unthinkable' as 'impossible, inconceivable': something that cannot happen or be true, and by extension 'ridiculous, absurd'. Usually written in kana alone; the natural choice for dismissing a possibility outright.

Use 「ありえない」 when something is impossible or beyond belief, 「とんでも無い」 when it is absurd or outrageous and you want to reject it, and 心外 when something wholly unexpected offends or disappoints you personally.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• とんでもないunthinkable
• 考えられないかんがえられないunthinkable
• とんでもunthinkable
• 図がないずがないunthinkable
• 考えもつかないかんがえもつかないunthinkable
• 問題外もんだいがいout of the question
• あり得べからざるありうべからざるinexcusable
• 心外しんがいunthinkable
• ありえないunthinkable
• あられもないunthinkable